General Stuff About Computer Networks
General Stuff About Computer Networks In the most generic sense, computer networks allow computers to share data, resources and applications. There are a 8 basic network topologies (Point-to-point, Bus, Star, Ring or circular, Mesh, Tree, Hybrid, Daisy Chain) basic types of networks are LANS (Local Area Networks) and WANS (Wide Area Networks) but there are many more. In their simplest form all networks have media, transport, and application layers. ''' '''Two common conceptual models for explaining these layers (OSI and TC/IP) are compared in an ugly table below. A really sweet table that shows all of the layers including the Logical Link and the Media Access Control sub layers can be seen at: Cross Layer Functions Table. We love to talk about this stuff in the Dojo. 'OSI' | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| 'TC/IP' | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| 'TCP/IP Protocols' |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Application | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| HTTP, FTP, Telnet, SMTP, DNS |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Presentation | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Application Layer | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Session | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Transport | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Transport Layer | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| TCP, UDP |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Network | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Network Layer | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| IP |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Datalink | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Network Interface | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| |- style="height:0px" | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Physical | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Network Interface | style="border:0px solid #000000;vertical-align:top;padding:0px 7px 0px 7px"| Ethernet, Token Ring, etc. |} No discussion of networks would be complete without discussing client-server software architecture model. It consists of two parts, client systems and server systems. Clients request data and servers serve the data. Sometimes one computer is the server AND the client process, this is called a single seat setup. The topic of computer networking is far too complex to cover in a one page overview but below are a number of concepts and links. 7 Layer OSI Model Application layer ' 'NNTPSIPSSIDNSFTPGopher HTTPNFSNTPSMPPSMTPSNMP TelnetDHCPNetconf(more) Process communications Internet Protocol (IP) computer network. Application layer protocols use the underlying transport layer protocols to establish connections. Presentation layer MIMEXDR It pretty much gets data ready (formatting, syntax etc.) for the Application layer. “Presentation”, get it? See what they did there? Session layer Named pipeNetBIOSSAPPPTPRTPSOCKSSPDYTLS/SSL Responsible for opening, closing and managing sessions Transport layer TCP UDP SCTP DCCP SPX Responsible for end to end communications services for applications Note: This layer is also in the TCP/IP model as well. Network layer IPIPv4IPv6 ICMPIPsecIGMPIPXAppleTalkX.25PLP This is where the packet forwarding and routing happens. Data link layer ATMARPSDLCHDLCCSLIPSLIPGFPPLIPIEEE 802.2http://en.wikipedia.org/wiki/Logical_link_controlL2TPIEEE 802.3Frame RelayITU-T G.hn DLLPPPX.25LAPBQ.921 LAPDQ.922 LAPF LLC and MAC sublayer Passes data to nodes correcting occasional physical layer errors when it can. ' 'Physical layer Basically hardware. Literally the physical link between network nodes. EIA/TIA-232EIA/TIA-449ITU-T V-SeriesI.430I.431PDHSONET/SDHPONOTNDSLIEEE 802.3IEEE 802.11IEEE 802.15IEEE 802.16IEEE 1394ITU-T G.hn PHYUSBBluetoothRS-232RS-449 Sweet Infographic This picture is worth 10K words courtesy Wikipedia General Network Admin Concepts Common Server Form Factors Tower Rack Mounted Blade User Rights Log on locally Change system time Shut down system Back up files and directories Restore files and directories Take ownership of files and alter objects Components of a Server Motherboard Processor Memory Hard Drives Network Connection Power Supply User Access/Permissions R Read W Write X Execute D Delete P Change O Ownership Network OS’s Core Functions Network Support File Sharing Services Multitasking Directory Services Security Services Security Open Door Type Closed Door Type General Network Admin Concepts Network Account Types Administrator User Guest Service Address Types Private Addresses Public Addresses Address Classes Class A Super Large Networks 8 bit Class B Pretty Large Networks 10 bit Class C 24 bits User Account Attributes User Passwords User Contact Info Account Restrictions Account Status Home Directory Dial In Permissions Group Membership Old School Networks Arpanet Milnet NSFnet NWLink Microsoft Network Stuff Active Directory Domain Controller Exchange Server Administrative Installation Image Group Policy NTFS New Technology File System Apple Network Stuff AppleTalk A List of Lists http://en.wikipedia.org/wiki/List_of_IP_protocol_numbers http://en.wikipedia.org/wiki/Lists_of_network_protocols http://en.wikipedia.org/wiki/List_of_networking_hardware_vendors http://en.wikipedia.org/wiki/Network_operating_system (s) http://en.wikipedia.org/wiki/List_of_unusual_deaths List of Common Terms/Quick Definition Logical Addressing Alternate to physical address viewed from the perspective of an application Digital Certificates Binds a public key to an identity Frame Relay A cheaper alternative to dedicated lines, sometimes causes overbooking Mirror An exact copy of data. A type of file synchronization Ping A network utility used to test round trip time and host availability on an IP network ' 'Data Encryption A huge security topic not lightly described in one sentence Protocol Stack A description of the layers media, transport, and applications (7 layers in OSI) SNA Systems Network Architecture Old School IBM Network Stack NAS Network Network Attached Storage An appliance used for file storage and serving ' 'Address Space A range of addresses with enough numbers to make it unique Port Port # + IP Address = A unique address to create a physical connection Client/Server Describes 1 or more computers, the server which shares resources with client. Directory A file system paradigm that references computer files or other directories IP Address Unique binary numbers (32 bit in IPv4and 128 bits in IPv6) assigned to a device. File Server A network computer whose sole function is to share files File System A data store that manages access to content and metadata. Firewall Hardware or software that analyzes data packets and keeps the bad guys out. License Server A fancy way of managing licenses NetBIOS Most commonly now NetBIOS over TCP/IP Protocol Analyzer Captures and analyzes signals and data traffic Sendmail Internetwork email routing facility. Supports SMTP among others Server Service Pack Subnet Subnet Mask (only 9 values possible (0,128,192,224,248,252,254,255) List of Standards Bodies Ansi American National Standards Institute IEEE Institute of Electrical and Electronics Engineers ISO International Organization for Standardization Common Acronyms WEP Wired Equivalent Privacy WEP2 Wired Equivalent Privacy WPA Wifi Protected Access BNC Cable Bayonethttp://en.wikipedia.org/wiki/BNC_connectorNeill–Concelman Cable ' 'CSMA/CD Carrier Sense Multiple Access Collision Detection CIDR Notation Classless Inter Domain Routing DNS Domain Name Server UDP User Datagram Protocol FAT File Allocation Table also TFAT32 FTP File Transfer Protocol HTTP Hypertext Transfer Protocol HTTPS HTTP_Secure IPX/SPXInternetwork Packet Exchange/Sequenced Packet Exchange TCP Transmission Control Protocol is a connection oriented transport protocol SMB System Management Bus SMTP Simple Mail Transfer Protocol SNMP Simple Network Management Protocol SSID Service Set Identifier VPN Virtual Private Network NIC Network Interface Cards KVM Switch Keyboard, Video Mouse RJ-45 ARP Address Resolution Protocol Converts IP addresses to MAC addresses IP Addresses Consist of a network part and a host part. IP is a routable protocol. UDP User Datagram Protocol MAC Media Access Control Common Hardware Terms Bridges, Routers, Switches and Hubs Backbone Connects various pieces of the network Repeater, Hub, Switch I’m using them interchangeably for brevity, they are physical layer devices used to connect other Ethernet devices Bridge Partition basically turns a large network into two smaller networks. Bridges are generally smart and can translate messages between different protocols in the physical layer. The bridges themselves exist in the network layer. Router a router is a node in it’s own on the network with it’s own MAC address and IP address. Node (simplified) a node is a connection point Segment A portion of the network Common Types of Networking Cables Who knew there were so many? Twisted Pair Cables Category 3 cable Category 4 cable Category 5 cable Category 6 cable EAD-socket Ethernet crossover cable Ethernet over twisted pair Networking cables Telecommunications cable More Stuff Ethernet Standard Ethernet Fast Ethernet Gigabit Ethernet Types of Firewall Packet Filtering Stateful Packet Inspection Circuit Level Gateway Certifications to look into A+ ''' '''Linux+ Network+ ''' '''Server+ Security+ ' '''MCTS ' 'MCITP ' 'MCSE ' '''MCSA Resources Used Networking for Dummies 10in1 Wikipedia OSI Model,TCP/IP Model ''' '''Method 1) Read the Dummies book taking extensive notes. ''' '''2) Transcribe notes and search terms in Wikipedia. 3) Read articles and define and summarize terms. ''' '''Additional Research (to do) Network Security http://network-security.alltop.com/ http://networkengineering.stackexchange.com/